• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.1145-1151
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• 2022

A hybrid cutting using both plasma and end mill was developed for safe and efficient dismantling of nuclear facilities. In this cutting method, a moving arc plasma heats up the workpiece before milling. Thermally softened part of the workpiece is then removed quickly and deeply with an end mill. For the cutting experiments, a three-axis numerical control (NC) milling machine was combined with a commercialized arc plasma torch and used to cut 25 mm thick stainless steel plates. Experimental results revealed that pre-heating by arc plasmas can improve the cutting volume per unit time higher than 40% by reducing the cutting load and increasing the cuttable depth when using an end mill without cutting fluids. These advantages of a hybrid cutting process are expected to contribute to quick and safe segmentations of metal structures with radioactively contaminated inner surfaces.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.162.1-162.1
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• 2015

The use of plasma has increased in bio-application field in recent years. Particularly, water treated by arc discharge or atmospheric pressure plasma has been actively utilized in bio-industry. In this study, we have developed a plasma activated water generating system. For this system, two kinds of plasma sources; dielectric barrier discharge (DBD) plasma and arc discharge plasma have been used. The discharge energy was calculated using the breakdown voltage and current, and the emission spectrum was measured to investigate the generated reactive species. We also analyzed the amount of reactive oxygen and nitrogen species in water using the chemical methods and nitric oxide sensor. Finally, the influence of plasma generated reactive species on the germination and growth of spinach (Spinacia oleracea) was investigated. Spinach is a green leafy vegetable that contains a large amount of various physiologically active organic compounds. However, it is characterized with a low seed germination rate.

• 전기의세계
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• v.24 no.6
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• pp.77-84
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• 1975

This paper treats A.C. arc movement in a transverse A.C. magnetic field at atmospheric pressure with the purpose of selecting electrode materials and obtaining detailed data for design of A.C. air circuit breaker, plasma accelerator and plasma jet. Arc velocities in transverse magnetic field are measured by varying arc current, arc voltage, gap length, magnetic flux density and the erosion of electrode surface, which influence arc velocities. The main results are; 1)Arc velocities in transverse magnetic field have different values according to electrodes of various materials and decrease in a descending order of cold cathode, medium cathode and hot cathode. 2)Arc velocities in transverse magnetic field increases with arc current, arc voltage, gap length and magnetic flux densith and on the other hand decrease with the increase of electrode surface erosion. 3)D.C.arc velocity in D.C. magnetic field is higher than A.C. arc velocity in A.C. magnetic field of the same value.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2701-2706
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• 2003

This paper describes weld seam tracking and error compensation methods of automatic plasma arc welding system designed for the corrugation panel that consists of a linear section and a curved section with various curvatures. Realizing automatic welding system, we are faced with two problems. One is a precise seam tracking and the other is an arc length control. Due to the complexity of the panel shape, it is difficult to find a seam and operate a torch manually in the welding process. So, laser vision sensor for seam tracking is equipped for sensing the seam position and controlling the height of a torch automatically. To attain more precise measurement of an arc length, we measure the 3D shape of the panel and analyze error factors according to the various panel states and caused errors are predicted through the welding process. Using that result, compensation algorithm is added to that of arc length control and real time error compensation is achieved. The result shows that these two methods work effectively.

• Journal of Welding and Joining
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• v.28 no.4
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• pp.67-72
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• 2010

The purpose of this paper is to understand the behavior of GHTAW process under the space environment with the experimental and numerical analysis. Gas Hollow Tungsten Arc Welding (GHTAW) using a hollow tungsten electrode was adopted, since the ignition and discharge of a conventional GTAW process is not appropriate to the space environment due to low pressure in space. In order to clarify the phenomena of GHTAW under space environment, an investigation of thermal and physical properties of the GHTAW arc plasma was experimentally performed under low pressure conditions. Furthermore, the molten pool behavior and weldment of GHTAW were understood by CFD-based numerical analysis, based on the models of GHTA heat source, arc pressure and electromagnetic force induced by arc plasma, the characteristics of which were obtained by the captured images of a CCD camera.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.12
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• pp.1240-1246
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• 2010

Enthalpy probe with the inner and outer diameters of 1.5 mm and 4.8 mm, respectively, is designed and used to measure the temperatures and velocities along the centerline of Ar arc plasma flow until the probe was destroyed. For this purpose, Ar arc plasma flow is generated by non-transferred type DC arc heater with the power level of 17 kW. From this experiment, it is shown that the designed enthalpy probe can measure the temperature and velocity of arc plasma flow up to 12,000 K and 600 m/s, respectively, without destroy of probe tip. In this extreme case, the arc plasma flow is calculated to transfer the heat flux of ${\sim}5{\times}10^7\;W/m^2$ to the probe based on the heat and thermal boundary equations near the forward stagnation point of a body immersed in arc plasma flow. Consequently, the designed enthalpy probe can measure the wide ranges of plasma temperatures, velocities and concentrations simultaneously, which are generated by various types of arc heaters within the heat flux ranges of $0{\sim}5{\times}10^7\;W/m^2$ on the probe tip.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.1
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• pp.8-16
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• 2023

In this work, we report basic performance test results of a lab-scale three phase alternative current (AC) arc plasma torch system for plasma gas reforming applications. The suggested system primarily consists of three graphite electrodes inclined at 12.5° to the central axis, a 𝞥 150 mm cylindrical gas path and a three phase-60 Hz AC power supply. At air flow rate of 50 Lpm and arc currents of 100-175 A, test results revealed that plasma resistances were decreasing from 1.08 Ω to 0.53 Ω with the increase of plasma power from 9.3 kW to 13.8 kW, causing the decrease of power factor and increase of the line voltages. However, the injected air can be heated quickly up to the temperatures of >1,200℃ when injecting AC arc plasma powers of >10 kW.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.4
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• pp.85-93
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• 2011

A parametric study is conducted for the design of segmented arc plasma torch with the input power and current of 0.4 MW and 300 A, respectively. For this purpose, we use the analytical relationship between input power, current condition, plasma temperature, inner diameter (R) and length (L) of the torch constrictor based on arc channel model. The results reveal that arc plasma temperatures increase monotonically as ��L increases or R decreases for the ranges of R ${\leq}$ 7.5 mm and L ${\leq}$ 1.25 m. For larger valuse of ��R and L than 7.5 mm and 1.25 m, respectively, however, they show non-linear behavior corresponding to the variations of ��L, which stands for the generation of unstable arc plasma. From this parametric study, optimum ranges of R and L are suggested as 5.5 mm ${\leq}$ R ${\leq}$ 7.5 mm and 0.25 m ${\leq}$ L ${\leq}$ 0.5 m for 0.4 MW class segmented arc plasma torch, under which stable arc plasma can be achieved at the input currents of ~300 A.

• 전기의세계
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• v.24 no.1
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• pp.75-85
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• 1975

In order to develop the commercial frequency (60Hz) plasma torch of small capacity for material cutting, welding and other industrial heating, the A.C plasma jet generator of non-transfered type is made domestically and the electrode configurations of plasma torch are composed of two kinds of electrodes W-C and W-Cu, combined by thermal emission and field emission electrode materials. In this paper, the characteristics of input power, thermal efficiency, electrode consumption, the flame and forms of arc voltage and arc current for A.C plasma torch are investigated in relation to such variables as arc current, argon flow and magnetic field intensity to obtain the basic design data necessary to A.C plasma jet generator. The result are as follows; (1)The input power, thermal efficiency and electrode consumption are influenced greatly by argon flow, magnetic field intensity and nozzle materials. (2)A.C arc voltage and current are non-symmetrial, involving D.C Component. Due to this current of D.C Component, transformer core is saturated and a large abnormal current flows into the primary winding coil. In order to prevent this abnormal current flow, a condenser must be connected in series to the main discharge circuit. (3)The stability and sharpness of jet flame are improved more in the torch of W-C electrode configuration than in the torch of W-Cu electrode configuration.

• Journal of Welding and Joining
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• v.30 no.2
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• pp.54-58
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• 2012

Al-coated steel sheets with excellent heat and corrosion resistance are widely used in various applications. In welding of thin plate, some defects such as unmelted zone and metal-through occur easily in the beginning and ending of welding line. In the study, the welding defects in Al-coated steel sheets were investigated with respect to plasma arc current, height between Cu block and base metals, and using a roller to align the height of the base metal. Full penetration and voids free welds were obtained with a plasma arc current 52A and weld speed 2.3m/min. An unmelted zone increased and Ericshen rate decreased as the height between Cu block and base metal increased from 0 to 0.6mm. Using a roller moving ahead of the plasma arc, the length of unmelted zone decreased from 1.7mm to 0.5mm.